The present invention relates to a plasma processing apparatus or a plasma processing method for processing a substrate-shaped sample such as a semiconductor wafer disposed in a processing chamber which is disposed within a vacuum vessel using plasma formed in the processing chamber, in particular, to a plasma processing apparatus or a plasma processing method for conducting etching processing on film layers disposed on a sample while supplying radio frequency power to electrodes within a sample stage on which the sample is mounted to machine it to predetermined profiles for electrodes, interconnections, and contact holes.
In manufacturing processes of semiconductor devices, thin film layers such as a polycrystalline Si film and an insulation film formed on a semiconductor wafer (substrate) to be processed are subjected to micro machining with dry etching to form gate electrodes and interconnections. In this apparatus for conducting dry etching machining, etching gas is introduced into the dry etching apparatus which is a vacuum vessel and a radio frequency electric field is introduced into the vacuum vessel to generate plasma. A thin film is etched by causing active species and ions generated in the plasma to be incident upon the wafer. As in etching, a mask such as a resist thin film having electrodes, interconnections, or hole patterns transcribed thereon is formed on an oxide film. In the dry etching, a poly-Si film, an insulation film, or the like is machined selectively with respect to the mask or an underlying layer and thereby a desired machined profile is formed.
In recent years, semiconductor manufacturing lines have become large in scale as the semiconductor market expands. Furthermore, in order to raise the productivity per unit area of the line from the viewpoint of the production cost, a semiconductor processing apparatus (multi-reactor) obtained by connecting to a transfer mechanism a plurality of processing vessels (reactors) each including a vacuum vessel having therein a processing chamber in which a wafer as a substrate-shaped sample to be processed is disposed and plasma for processing the wafer is formed is mainly used.
In addition, as the scale of the manufacturing line becomes large, execution of processing is conducted on wafers which have the same dimension and structure and which can be considered to comply with the same specifications in a plurality of semiconductor processing apparatuses with respect to one process of wafer processing. Such execution of substantially the same processing in a plurality of apparatuses in a manufacturing line is conducted in dry etching processing as well.
For improving the yield in the manufacturing line of semiconductor apparatuses such as semiconductor devices, it is demanded in semiconductor manufacturing apparatuses such as etching apparatuses, which execute various processes in manufacturing respectively, that processing is conducted to make characteristics and results of processing more uniform in the in-plane direction of the wafer and that differences in machining results among a plurality of wafers are small. For example, in a dry etching apparatus, it is demanded that characteristics such as the density and intensity of plasma generated in the reactor have high uniformity in the in-plane direction of the wafer. In addition, it is demanded that the plasma density can be made a predetermined value or more, for example 1010/cm3 or more, to improve the processing rate (speed), that stable plasma can be formed when the pressure of gas during processing in the processing chamber is an appropriate pressure in the range of an extremely low pressure to a high pressure (for example, 0.1 to 100 Pa) for improving the controllability of the profile obtained as a result of machining, although it depends upon the conditions of the processing process (step), or the like. In addition, it has been demanded to make variations smaller in plasma density and pressure among various wafers or among various reactors and semiconductor manufacturing apparatuses.
As miniaturization advances, nearly equivalent process performances (characteristics such as a processing rate and machining precision) are obtained among respective reactors in a plurality of semiconductor manufacturing apparatuses by optimizing the processing conditions in respective reactors equipped in respective apparatuses corresponding to demanded specifications; however, the processing conditions, that is, the so-called processing recipes must be managed for every reactor and development is needed to select and determine such conditions. Furthermore, since the pattern of an exposure mask is optimized to conform to the processing conditions in an etching apparatus additionally, it is demanded to minimize the differences in conditions in processing chambers among respective reactors with high precision.
In this way, in the manufacturing line of the semiconductor devices one which yields the same performance and result when wafers according to equivalent specifications are processed at the same conditions in a plurality of reactors or a plurality of processing apparatuses is demanded. Hitherto, therefore, improvement of precision in dimensions and arrangements of components which constitute reactors and management for adjusting the performance and characteristics of the respective reactors to bring them into desired ranges have been conducted.
When miniaturization of semiconductors has further advanced as in recent years, however, a further high precision is demanded on management of individual parts and performance management. For further improving the precision of dimensions of parts and arrangement distances, however, a longer time and a higher cost as compared with the present time will be needed, resulting in a hampered rate of operation and running cost of the apparatus. On the other hand, if the precision of them is not sufficient, differences in the aforementioned dimensions and distances and the differences in processing characteristics and profiles and dimensions obtained as a result of machining wafers become large among different reactors when a semiconductor manufacturing apparatus or reactors are assembled, and they depart from desired process specifications.
In conventional techniques of the etching apparatus, various contrivances have been made to obtain stable plasma having high reproducibility which is needed to solve such problems. For example, in JP-A-7-065993, it is disclosed that one which detects light emission from plasma and acquires data at periods of a high rate (in the range of 100 Hz to 10 MHz) and controls a microwave stub tuner to minimize the change of the light emission in time in order to obtain stable plasma. In addition, in JP-A-2004-281442, in order to obtain the same etching performance repetitively a plasma processing apparatus which controls microwave power to cause a bias voltage applied to a wafer to always take a minimum value is disclosed.
Furthermore, in JP-A-2001-110784, a plasma processing apparatus which estimates the conditions in a processing chamber and adjusts the operation of the plasma processing apparatus to attain desired conditions based on a process model acquired in advance from a spectrum at a specific wavelength which is obtained by detecting light emission from plasma is disclosed. Incidentally, in Mineo Furuse et al., Japanese Journal of Applied Physics, Vol. 36, pp. 4617-4619, a technique of installing a probe within a processing chamber, detecting electric field intensity distribution in a space where plasma is generated, and detecting a change of characteristics of the plasma is disclosed.